Light beam interrupt detection apparatus are used in a wide variety of applications to detect the motion and position of objects without physically disturbing the object whose movement or position is detected. Under certain circumstances, namely when either the light source creating the light beam or the light receiver detecting the light beam or both are connected to a surrounding object or environment which is vibrating or being vibrated, the reliability of the interrupt detection is compromised. Obviously, a small vibration causing a change in angle of the light source placed at a great distance from the light receiver will cause the light beam to miss the light receiver.
When operating in a vibrating environment, it is known to use a light beam which is sufficiently large that as the beam wanders during vibrations, sufficient light is received by the receiver such that an interrupt by an object can be detected. A larger beam however requires a larger light source and will consume more power at the light source for generating a larger beam.
Also, using a smaller receiver with a wider beam, which will help keep the beam on the receiver in order to operate in a vibrating environment, will reduce the amount of useable signal from the light receiver since less light is received, possibly decreasing the signal to noise ratio at the receiver and lowering the reliability of the interrupt detection.
It is therefore an object of the invention to provide a light beam interrupted detection apparatus for use in a vibrating environment which is able to use a minimum power light source without compromising the reliability of the interrupt detection.